Add filterAndJoin() and classes() helpers.

PiperOrigin-RevId: 576560779

java/src/com/google/template/soy/basicfunctions/BasicFunctions.java

@@ -29,8 +29,10 @@ public static ImmutableList<SoySourceFunction> functions() {
         // go/keep-sorted start
         new BooleanFunction(),
         new CeilingFunction(),
+        new ClassesFunction(),
         new ConcatListsFunction(),
         new ConcatMapsMethod(),
+        new FilterAndJoinFunction(),
         new FloorFunction(),
         new HtmlToTextFunction(),
         new IsFiniteFunction(),

java/src/com/google/template/soy/basicfunctions/BasicFunctionsRuntime.java

@@ -492,4 +492,17 @@ public static boolean isFinite(SoyValue arg) {
   public static boolean booleanFunc(SoyValue value) {
     return value != null && value.coerceToBoolean();
   }
+
+  /** Joins items with a delimiter, filtering out falsey values. */
+  public static String filterAndJoin(String delim, List<SoyValue> values) {
+    return values.stream()
+        .filter(SoyValue::coerceToBoolean)
+        .map(SoyValue::coerceToString)
+        .collect(joining(delim));
+  }
+
+  /** Joins items with a space, filtering out falsey values. */
+  public static String classes(List<SoyValue> values) {
+    return filterAndJoin(" ", values);
+  }
 }

java/src/com/google/template/soy/basicfunctions/ClassesFunction.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2023 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.template.soy.basicfunctions;
+
+import com.google.template.soy.plugin.java.restricted.JavaPluginContext;
+import com.google.template.soy.plugin.java.restricted.JavaValue;
+import com.google.template.soy.plugin.java.restricted.JavaValueFactory;
+import com.google.template.soy.plugin.java.restricted.SoyJavaSourceFunction;
+import com.google.template.soy.plugin.javascript.restricted.JavaScriptPluginContext;
+import com.google.template.soy.plugin.javascript.restricted.JavaScriptValue;
+import com.google.template.soy.plugin.javascript.restricted.JavaScriptValueFactory;
+import com.google.template.soy.plugin.javascript.restricted.SoyJavaScriptSourceFunction;
+import com.google.template.soy.plugin.python.restricted.PythonPluginContext;
+import com.google.template.soy.plugin.python.restricted.PythonValue;
+import com.google.template.soy.plugin.python.restricted.PythonValueFactory;
+import com.google.template.soy.plugin.python.restricted.SoyPythonSourceFunction;
+import com.google.template.soy.shared.restricted.Signature;
+import com.google.template.soy.shared.restricted.SoyFunctionSignature;
+import com.google.template.soy.shared.restricted.SoyPureFunction;
+import java.lang.reflect.Method;
+import java.util.List;
+
+/** Joins items with a space, filtering out falsey values. */
+@SoyPureFunction
+@SoyFunctionSignature(
+    name = "classes",
+    value =
+        @Signature(
+            parameterTypes = {"list<string | bool | null | undefined>"},
+            returnType = "string"))
+public final class ClassesFunction
+    implements SoyJavaSourceFunction, SoyJavaScriptSourceFunction, SoyPythonSourceFunction {
+
+  @Override
+  public JavaScriptValue applyForJavaScriptSource(
+      JavaScriptValueFactory factory, List<JavaScriptValue> args, JavaScriptPluginContext context) {
+    return factory.callNamespaceFunction("soy", "soy.$$classes", args.get(0));
+  }
+
+  @Override
+  public PythonValue applyForPythonSource(
+      PythonValueFactory factory, List<PythonValue> args, PythonPluginContext context) {
+    return factory.global("runtime.classes").call(args.get(0));
+  }
+
+  // lazy singleton pattern, allows other backends to avoid the work.
+  private static final class Methods {
+    static final Method CLASSES_FN =
+        JavaValueFactory.createMethod(BasicFunctionsRuntime.class, "classes", List.class);
+  }
+
+  @Override
+  public JavaValue applyForJavaSource(
+      JavaValueFactory factory, List<JavaValue> args, JavaPluginContext context) {
+    return factory.callStaticMethod(Methods.CLASSES_FN, args.get(0));
+  }
+}

java/src/com/google/template/soy/basicfunctions/FilterAndJoinFunction.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2023 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.template.soy.basicfunctions;
+
+import com.google.template.soy.plugin.java.restricted.JavaPluginContext;
+import com.google.template.soy.plugin.java.restricted.JavaValue;
+import com.google.template.soy.plugin.java.restricted.JavaValueFactory;
+import com.google.template.soy.plugin.java.restricted.SoyJavaSourceFunction;
+import com.google.template.soy.plugin.javascript.restricted.JavaScriptPluginContext;
+import com.google.template.soy.plugin.javascript.restricted.JavaScriptValue;
+import com.google.template.soy.plugin.javascript.restricted.JavaScriptValueFactory;
+import com.google.template.soy.plugin.javascript.restricted.SoyJavaScriptSourceFunction;
+import com.google.template.soy.plugin.python.restricted.PythonPluginContext;
+import com.google.template.soy.plugin.python.restricted.PythonValue;
+import com.google.template.soy.plugin.python.restricted.PythonValueFactory;
+import com.google.template.soy.plugin.python.restricted.SoyPythonSourceFunction;
+import com.google.template.soy.shared.restricted.Signature;
+import com.google.template.soy.shared.restricted.SoyFunctionSignature;
+import com.google.template.soy.shared.restricted.SoyPureFunction;
+import java.lang.reflect.Method;
+import java.util.List;
+
+/** Joins items with the specified delimiter, filtering out falsey values. */
+@SoyPureFunction
+@SoyFunctionSignature(
+    name = "filterAndJoin",
+    value =
+        @Signature(
+            parameterTypes = {"string", "list<string | bool | null | undefined>"},
+            returnType = "string"))
+public final class FilterAndJoinFunction
+    implements SoyJavaSourceFunction, SoyJavaScriptSourceFunction, SoyPythonSourceFunction {
+
+  @Override
+  public JavaScriptValue applyForJavaScriptSource(
+      JavaScriptValueFactory factory, List<JavaScriptValue> args, JavaScriptPluginContext context) {
+    return factory.callNamespaceFunction("soy", "soy.$$filterAndJoin", args.get(0), args.get(1));
+  }
+
+  @Override
+  public PythonValue applyForPythonSource(
+      PythonValueFactory factory, List<PythonValue> args, PythonPluginContext context) {
+    return factory.global("runtime.filter_and_join").call(args.get(0), args.get(1));
+  }
+
+  // lazy singleton pattern, allows other backends to avoid the work.
+  private static final class Methods {
+    static final Method FILTER_AND_JOIN_FN =
+        JavaValueFactory.createMethod(
+            BasicFunctionsRuntime.class, "filterAndJoin", String.class, List.class);
+  }
+
+  @Override
+  public JavaValue applyForJavaSource(
+      JavaValueFactory factory, List<JavaValue> args, JavaPluginContext context) {
+    return factory.callStaticMethod(Methods.FILTER_AND_JOIN_FN, args.get(0), args.get(1));
+  }
+}

javascript/soyutils_usegoog.js

@@ -1849,6 +1849,27 @@ const $$insertWordBreaks = function(value, maxCharsBetweenWordBreaks) {
   return result;
 };
 
+/**
+ * Joins items with a delimiter, filtering out falsey values.
+ * @param {string} delim The delimiter to join on.
+ * @param {...string|boolean|null|undefined} values The values to join.
+ * @return {string} The joined string.
+ */
+const $$filterAndJoin = function(delim, ...values) {
+  return values.filter((s) => s).join(delim);
+};
+
+
+/**
+ * Joins items with a space, filtering out falsey values.
+ * @param {...string|boolean|null|undefined} values The values to join.
+ * @return {string} The joined string.
+ */
+const $$classes = function(...values) {
+  return $$filterAndJoin(' ', ...values);
+};
+
+
 /**
  * Conditionally concatenates two attribute values with a delimiter if they are
  * both non-empty.
@@ -2626,6 +2647,8 @@ exports = {
   $$insertWordBreaks,
   $$concatAttributeValues,
   $$concatCssValues,
+  $$classes,
+  $$filterAndJoin,
   $$truncate,
   $$listContains,
   $$listIndexOf,

python/runtime.py

@@ -679,6 +679,31 @@ def soy_round(num, precision=0):
   return rounded_number
 
 
+def filter_and_join(delim, values):
+  """Joins items with a delimiter, filtering out falsey values.
+  
+  Args:
+    delim: The delimiter to use.
+    values: The values to join.
+
+  Returns:
+    The joined string.
+  """
+  return delim.join([x for x in values if x])
+
+
+def classes(values):
+  """Joins items with a space, filtering out falsey values.
+
+  Args:
+    values: The values to join.
+
+  Returns:
+    The joined string.
+  """
+  return filter_and_join(' ', values)
+
+
 ######################
 # Utility functions. #
 ######################